A wave of nausea washed over Marcie Iseli shortly after her CT scan finished. Then her head started to feel strange, as if heat was emanating from somewhere deep inside. Her face started to feel uncomfortably warm, like she’d been sunburned.

She’d gone in for the brain scan because of headaches and nerve pain on one side of her face, but now doctors had no idea what was wrong with her — especially since the scan showed no abnormalities. Two weeks later, clumps of her hair started falling out, followed by debilitating fatigue and problems with balance and memory.

“I lost a 4-inch wide strip of hair that went from one side of my head to the other, recalls the 36-year-old mother of two from Kenova, W.Va. “I went to my family physician and then to a dermatologist who said he’d never seen anything like it.”

It was two months before Iseli learned the cause of her mysterious symptoms: She’d gotten an overdose of radiation during the scan of her head, a blast almost eight times the expected amount.

Within minutes, Iseli became a victim of radiation poisoning, with some of the same symptoms and possible long-term effects that may face workers now exposed to high levels of radiation at Japan’s ailing Fukushima Daiichi nuclear plant.

While Iseli’s targeted medical overdose is not the same as the full-body blast of a nuclear accident, it does offer some insight into the experience of radiation exposure, doctors say.

“When you overload the system, you’re going to get in trouble,” said Dr. Reuben Mezrich, a professor of diagnostic radiology and nuclear medicine at the University of Maryland School of Medicine.

Classic symptoms
Iseli’s symptoms are classic for acute radiation syndrome, but with one big difference, said Andrew Maidment, an associate professor of radiology and chief of physics at the University of Pennsylvania.

“People in the power plant are likely to be exposed all over their bodies,” Maidment says. “Whereas she was exposed only to the head, their livers, lungs and heads will all be exposed.”

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

That’s evident in the precise swath of hair that Iseli lost. It followed the path of the radiation beam, which damaged the hair follicles.

Iseli was supposed to receive 500 milligrays of radiation during her brain scan, but instead received a 3,875-milligray dose, according to Richard A. Patterson, an attorney who is representing Iseli and others who were overdosed in a spate of medical errors that resulted in a federal investigation.

One milligray absorbed by the whole body is equivalent to 1 millisievert, experts said. At one point, Japanese officials said several dozen workers at the Fukushima plant were exposed to levels detected at 400 millisieverts per hour, which later dropped. For the workers to get a similar dose to what Iseli received, they would have had to stand in the path of that level of radiation for 10 hours, Mezrich said.

“If it was going at that full rate and they were standing right in the middle of it, not hiding behind a wall or a column, if someone was exposed to that for a full day, they are absolutely at risk for having damage,” he added.

The actual exposure to the workers remains unclear. It depends on how the radiation levels varied and what kind of protective gear the workers had. And the worst effects likely will be limited to those in very close proximity to the source of radiation, perhaps affecting the so-called Fukushima 50, workers who stayed behind to grapple with the failing plant. About 120 other workers were evacuated earlier, according to Japanese officials.

At the lowest levels of exposure, nuclear plant employees wouldn’t notice any symptoms, Maidment says. But there might be minor chromosomal changes in cells in the blood.

How much radiation is dangerous?

Radiation is measured using the unit sievert, which quantifies the amount of radiation absorbed by human tissues. One sievert is 1,000 millisieverts (mSv).

In the U.S., the average person is exposed to about 6.2 millisieverts a year, mostly from background radiation and medical tests.

Facts about radiation exposure:

A person would need to be exposed to at least 100 mSv a year to have an increase in cancer risk. Exposure to 1,000 mSv during a year would probably cause a fatal cancer many years later in five out of every 100 people.

Sources: Reuters; New England Journal of Medicine; American Cancer Society; World Nuclear Association and Taiwan's Atomic Energy Council

“The next level up, they would be experiencing nausea and vomiting,” Maidment said. “And this level is typically associated with some bone marrow suppression. The next level up you get leucopenia, where there are an insufficient number of white blood cells produced, and you might start to see skin burns and hair loss. The next level you get a GI syndrome, where cells start to slough off and the gut has trouble taking in nutrients. At the highest doses you can get brain death or cardiovascular collapse.”

Iseli’s symptoms, while debilitating, did not rise to that level of severity. The fatigue that Iseli has experienced could be due to bone marrow suppression which can occur with a radiation overdose.

“You get fewer blood cells and thus less oxygen,” Maidment explained.

Despite the threat posed by radiation, treatment options are few. Iseli discovered her overdose too late, but even if technicians had noticed it quickly, there was not much they would have done, noted Mezrich.

A patient like Iseli might have been given potassium iodide, depending on her exposure, to protect her thyroid gland from absorbing radioactive iodine and perhaps some steroid cream to ease the burning and itching of her skin.

The same goes for workers at the plant in Japan, even those exposed to high levels of radiation. Doctors would treat the victims for symptoms, rehydrating with fluids, for instance, and treating any gastrointestinal distress in usual ways.

'No magic potion'
The U.S. Centers for Disease Control and Prevention lists four potential treatments for radiation poisoning, including potassium iodide to protect the thyroid. There’s also Prussian blue, a blue dye that binds to radioactive materials cesium and thallium and prevents them from being reabsorbed by the body.

The CDC also lists DTPA, a medicine called a chelating agent, which also binds and holds radioactive materials, allowing them to be eliminated from the body. It’s best used soon after radioactive material has entered the body. Finally, there’s Neupogen, the brand name for filgrastim, a cancer drug that boosts formation of white blood cells. Some experts believe treating radiation victims with Neupogen can help stave off infection while their own bone marrow recovers.

Except for the potassium iodide, none of these treatments is universally used, Mezrich noted

“There is no magic potion,” he said.

In Japan, officials continue to monitor workers and the public for signs of radiation exposure. Widespread illness likely won’t affect the general population.

“You wouldn’t expect them to demonstrate symptoms of acute radiation syndrome,” Maidment says. “What happens as the plant burns is that radioactive materials are released either as gases or dust which are blown around by the wind and eventually settle on the surrounding area.”

Most of the radioactive material that is blown around is Iodine-131, which can impact the thyroid, Maidment says. There might be a rise in the number of people who develop thyroid cancer as a result of the fallout. However, Maidment noted, thyroid cancer is very curable.

Video: Officials disagree on level of nuclear danger

Transcript of: Officials disagree on level of nuclear danger

SAVANNAH GUTHRIE, co-host:NBC
's chief science correspondent,
Robert Bazell
, is in
Tokyo
this morning.
Bob
, good morning. I know there was a news conference this morning from Japanese officials, and these Japanese officials said there was disagreement even among themselves as to whether or not that storage pool with those expired fuel rods was empty. My question to you is, if the Japanese officials can't even agree amongst themselves, what does that tell us about their credibility and the handle they have on this situation?

ROBERT BAZELL reporting:Good morning,
Savannah
. I've just came from that news conference, and there's almost no credibility left. And this is, as we're hearing, a very ominous situation. There's six reactors 170 miles north of here. At least four of them are way out of control and could release a lot of radiation at any time. They are hundred -- there's -- the wind is now blowing in this direction toward an area where 100 -- where 30 million people live, so it's very serious. I'm not saying there's going to be a release of radiation, but it certainly could happen.

GUTHRIE:And what are people in
Japan
telling you? How do they feel about their
government
, this lack of information and, maybe even worse, a lack of candor from the
government
?

BAZELL:Well, there -- a lot of people are getting frustrated and upset, and I'm telling you it's not just Japanese citizens, a lot of nuclear experts. I've been covering this story all week and I've talked to experts here in
Japan
and
Europe
and in the
United States
. And a lot -- at first a lot of them were very reassuring about this situation, but now they say they feel like they've been betrayed. They're sickened because they say -- they think the company that owns the plants probably was doing something wrong, and that's lead -- making it so difficult to bring it under control now. Because it wasn't just the tsunami, it wasn't just the earthquake. Those are horrible, but there are difficulties they'd -- are seem to be caused because the company was making some shortcuts before.

GUTHRIE:And,
Robert
, as I understand it, Japanese officials are still saying there's no need to leave
Tokyo
. At this point are people still listening to that advice from the
government
, or are you starting to see a mad scramble from the city?

BAZELL:Well, there's a lot of people who are leaving if they can,
Japanese people
. Of course, many of them don't have a place to go or the means to leave. A lot of foreigners, as
Ann
pointed out in her piece, are leaving. It's also very quiet here for a different set of reasons, which are related to the earthquake. There's almost no gasoline, there's rolling black -- power blackouts, and the trains aren't running. So a lot of people can't make it to work and a lot of businesses are closed. So it's a very, very quiet time here in
Tokyo
.